Capillary electrophoresis (CE) instruments use electric fields to separate molecules within narrow-bore capillaries (typically 20-100 μm internal diameter). CE techniques are employed in numerous applications, including DNA sequencing, nucleotide quantification, and mutation/polymorphism analysis. Samples analyzed by CE are often detected by fluorescence emission of the sample which has been tagged with a fluorophore. The fluorophores are excited with a light source, and the intensities of the fluorescence emission represent the concentration or amount of the sample components. Generally, the light source is focused on a narrow point on the sample to maximize the energy available for the excitation of fluorophore within the illuminated volume. The detector, which is usually a photomultiplier, photodiode, diode array, or CCD, is positioned to capture the maximum amount of light from the sample, without specific discrimination of the capillary walls or the background.